Port forwarding only working for one of my friends, two others receive "getsockopt"
So, I spent an afternoon setting up forge's local server hosting, for a 1.20.1 modpack, and it works when I connect to the server via my public IP address, and one of my friends (who doesn't live in the same house as me), can connect to the server via the public IP from my ISP, and I can use the same IP to join too, even without using localhost as the address. The problem arises with two other friends, who both cannot join using the same address, instead getting "Connection timed out: getsockopt" or something similar. They've tried many things on their end, such as disabling IPv6, ipconfig /flushdns (plus a few other command prompt entries), allowing both private and public things for Java in the windows firewall, and nothing works. Every time, they receive the same error, which is weird considering one of them can actually join. The only thing that allows them to join, is if I use a third party port forwarder, like playit.gg, but it's an extreme annoyance to boot up like 4 different things, just so me and a few friends can play for like an hour a day. Is there any possible way to fix this, and if so, is the issue on my end, or their ends? Another thing that could help to note, is that if they try add the server onto their server list (they as in the two who can't connect), the ping bar alternates between blue and grey for probably 20s before saying something in red text like "Cannot connect to server" or something. They can play other servers fine like Hypixel and stuff, just not mine for some reason. Also, I'm on Windows 10, the other 3 are on Windows 11, but I don't think that'd really change much, considering one who's on windows 11 can join regardless.
P.S, I followed TheBreakdown's youtube tutorial, and his website tutorial on port forwarding for most of the process. I am assuming there's an issue with my ISP's port forwarding, but I'm not sure what it could be considering me and one friend can join, but two others can't. We are all running the same modpack, "Fear Nightfall: Remains of Chaos" in 1.20.1
LOG: https://mclo.gs/w6eS08G